Xerographic printer



July 5, 1960 w. D. BOLTON XEROGRAPH'IC PRINTER Original Filed Dec. 21, 1955 3 Sheets-Sheet 1 MECHANISM RECORD CARD CONTROLLED DATA INPUT DRIVE MECHANISM 'FIG. .1.

TONER IMAGE FIXING APPARATUS 31 VARIABLE SPEED CONTROL IN V EN TOR D BOLTON WALLIS TTOR NEY uly 5, 19 w. D. BOLTON 2,944,147

XEROGRAPHI C PRINTER Original Filed Dec. 21, 1955 3 Sheets-Sheet 2 ARC CONTROLS CiRCU ITS 57 July 5, 1960 w. D. BOLTON XEROGRAPHIC PRINTER 3 Sheets-Sheet 5 Original Filed Dec. 21, 1955 DRIVE MECHANISM W GENEVA RECOR D CAR D CONTROLLED DATA IN PUT MECHANISM Un d? seesinPe e O 2,944,147 xnnonnarnrc PRINTER Wallis DgBolton, Vestal,N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Original application Dec. 21, 1955, Set. No. 554,513. Divided and this application Sept. 23, 1957, Ser. No. 685,741

2 Claims. Ci. 250 mm machinecommonly referred to as a xerog'i'aphic printer.

As is well known to persons familiar with this phase of the graphic art, xerography is a term applied to a printing process in which latent electrostatic images are rendered visible, i.e., developed, by a pigmented electroscopic powder, often referred to as xerographic toner, the resulting electroscopic powder image thereafter first being transferred and then afiixed to a print receiving sheet so as to afford a permanent printed copy which depicts the latent electrostatic image exactly. An apparatus employing such a printing process is shown and described in Carlson Patent No. 2,357,809, which issued on September 12, 1944, and follows the steps of electrically charging an el'ectrophotoplate having a photoconductive insulating layer on an electrically conductive backing member, exposing the charged electrophotoplate to an optical image so as to form a latent electrostatic image thereof on the electrophotoplate, dusting the latent electrostatic image with xerographic toner in order to develop this latent image so that the configuration thereof is rendered visible, transferring the xerographic toner image onto a print receiving sheet such as paper, and finally removing any excess toner which remains on the surface of the electrophotoplate after the preceding transfer step but prior to the next electrophotoplate charging step.

Another kind of xerographic printer employing a printing process somewhat different from the aforementioned one disclosed by the Carlson patent,'is shown and described in Schaffertlatent No. 2,576,047, which issued on November 20, 1951. This printing machine embodies 'a continuously rotating drum on which an electrically insulating image layer is secured. This permanent design image layer is electrostatically charged prior to being dusted with xerographic toner. Thetoner will, of course, be attracted and adhere to the charged surface area of the permanent design image layer so that when the toner supported thereby is transferred onto a print receiving sheet, the xerographic toner so transferred will define a a Before proceeding any further it would be well to distinguish an electrophotoplate from an electroplate. The former is a member comprising a photoconductive insulating layer on a conductive backing, whereas the electroplate is a member comprising an insulating layer, photoelectric and otherwise, on a conductive backing. Accordingly, it should be clear that the expression electroplate' includes an electrophotoplate. For this reason, the term electroplate will be used throughout this specification.

Most xerographic printers known heretofore are substantially similar to those described in the aforementioned Carlson and Schaffert patents in that they are for the most part copying and/or duplicating machines. That is, the latent electrostatic image of some given object is generally formed by way of an optimal image thereof, which image is subsequently developed and then printed in the well-known manner. It is the purpose of the present invention to provide an original document xerographic printer which does not require optical image apparatus for producing the latent electrostatic images. Instead, this latter-mentioned xerographic printer causes symbols, characters and numerals to be formed in a line-by-line fashion directly in response to data representing signals. Briefly, latent electrostatic images of symbols, characters and numerals are formed on the surface of an electroplate by directing electrostatic field discharges, known commonly as corona currents, having configurations corresponding to these data, onto the electroplate surface. This is accomplished by employing a so-called data stencil cylinder forshaping the aforesaid field discharges selectively in accordance with incoming data representing signals. These signals might be transmitted from a calculator, for example, as well as from a record card or tape reader.

Accordingly, the object of this invention is to provide an improved latent electrostatic image producing apparatus. 1

Another object of this invention is to provide an improved mutable data xerographic printer.

Still another object of this invention is to provide an i 7 improved line-by-line Xerographic printer.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a diagrammatic view of a continuously operating xerographic printer employing brush development.

Fig. 2 is a diagrammatic view of the apparatus used to govern the forming of latent electrostatic images on the xerographic drum of the printer.

Fig. 3 is a somewhat diagrammatic view of optical apparatus used to form latent electrostatic images on the xerographic drum of the printer.

Figs. 4 through 6, inclusive, are somewhat diagrammatic views of non-optical apparatus used to form latent electrostatic images on the xerographic drum of the printer.

General description Shown in Fig. 1 is a xerographic printer in which the present invention can be utilized. The metal cylinder 10 of xerographic drum 11 is mounted for rotation on a drive shaft 12 which is driven in a counterclockwise direction 'by an electric motor (not shown) Within drive mechanism 13 via aconventional Geneva mechanism 14. This drum 11 has secured thereto an electroplate 16 which includes an insulating layer 17 of amorphous selenium, for example, on an electrically conductive backing member 18 of aluminum, for instance. The 'electroplate 16 is flexed around cylinder 10 as shown, and is attached thereto in any one of the numerous conventional waysof attaching a printing plate to a supporting cylinder. It is important,

Patented- July 5, 1960 PM 2,944,147 V I r however, that in what ever manner this attachment is made, the backing member 18 be in intimate contact with the insulating layer 17 as well as in good electrical contact with the drum cylinder which is connected to ground potential via shaft 12.

As successive incremental areas of the insulating layer 17 are moved in a counterclockwise direction past ionproducing charging unit 19 of the type shown and described inlCarlson Patent No. 2,588,699, issued on Mar. 11, 1952, the aforesaid layer 17 of dielectric materialis electrostatically charged positive. These positively charged incremental areas are then moved past an optical image producing unit 21 (see also Fig. 3) which projects optical images of the text or matter to be copied, onto the electrically charged surface of photoconductive insulating layer 17. The apparatus by which the optical images are produced and projected onto the surface of layer 17 of electroplate 16, will be described shortly.

Consequentupon the exposure of the photoconductive insulating layer 17 to the optical images produced by and directed from optical unit 21, latent electrostatic images thereof are produced on electroplate 16. This is for the reason that those electrically charged incremental areas of insulating layer 17 onto which light rays are directed, are discharged, whereas those areas not illuminated by light rays remain charged. Hence, after the positively charged electroplate 16 is exposed to the aforesaid optical images, positive latent electrostatic images thereof corresponding to the optical information projected onto the surface of xerographic drum 11, will remain.

Continued rotation in a counterclockwise direction will cause the latent electrostatic images appearing on electroplate 16 of drum '11 to be moved into a latent electrostatic image developing chamber 22. This chamber is described in detail in application Ser. No. 554,513 and is one wherein xerographic toner of the general type described in Copley Patent No. 2,659,670 which issued on Nov. 17, 1953, is applied to the exposed surface of electroplate 16, and, of course, over the latent electrostatic images thereon. As a result, the pigmented toner particles will adhere to only the afore-mentioned image defining charged areas of electroplate 16, whereby a corresponding number of developed toner images which now visibly define their respective latent electrostatic images appear on'the surfaceof the electroplate.

A still further counterclockwise rotation of xerographic drum 11 will cause the toner images developed on the surface of electroplate 16, to move out of developing chamber 22 and into the realm of a negative ion-producing unit 23' which is similar to afore-mentioned unit 19. The effect of this second electrostatic field produced by unit 23 is to decrease somewhat the magnitude of the image defining positive electrical charge stored in nonconducting layer 17. This is to condition the developed toner. images being carried on the'surface of electroplate 16 for ready transfer onto a print receiving web 24. In addition thereto, the negative electrostatic field to which the photo-conductive insulating layer 17 is subjected, corrects an unfavorable condition known generally as selenium fatigue.

Further rotation of drum 11 causes the developed toner images thereon to move-into a xerographic toner image transfer, or printing, station, whereat a transfer roller 26 comprising a metallic conductive portion 27 and an outer portion'28 of a very resilient material having a high electrical resistance of at least 10 power ohms per cubic centimeter,'is used to transfer the xerographic toner images from the surface ofelectroplate 16 onto the surface of print receiving web 24. The transfer roller 26 is similar to oneshown and described in detail in copending U.S. patent application Serial No. 419,314, filed by C. I. Fitch on'Mar. 29, 1954, 'now U.S. Patent 2,807,233, issued on Sept. 24, 1957. For this'reason, the same will not be describedin' detail herein. The print receiving web 24, which is preferably a paper strip, is advanced by conventional means (not shown) from a web supply roll 29 to a web take-up roll 30 via the afore-mentioned transfer station whereat transfer roll 26 is located, and a toner image fixing station 31. The positive potential applied to transfer roller 26 causes the xerographic toner particles on the drum surface and which define the latent electrostatic images, to migrate from the surface of electroplate 16 to the opposite surface of print receiving web 24. It might be well to mention here that web 24 is advanced at a lineal speed that corresponds to the peripheral speed of xerographic drum 11.

In order to remove any excess xerographic toner particles that might remain on the surface of electroplate 16 after the toner image transfer but prior to charging the incremental areas of the photoconductive insulating layer 17 again by ion-producing unit 19 during another machine cycle, a rotating brush cleaning roller 32 is positioned within a housing 33 for retaining the toner so removed from the surface of electroplate 16 by roller 32. A vacuum cleaner unit (not shown) may also be utilized within the housing 33 in order to remove the xerographic toner caused to be accumulated therein. As is shown in Fig. 1, prior to subjecting the incremental areas of the photoconductive insulating layer 17 to the cleaning action of plush roller 32, the electroplate 16 is preferably subjected to another negative electrostatic field produced by corona unit 34 which is similar to afore-mentioned unit 23. A beam of light rays from a source 36 is also projected onto the surface of electroplate 16 so as to assure discharge of all of the areas of the photoconductive insulating layer 17. The negative field produced by unit 34 tends to avoid the previously mentioned unfavorable condition selenium fatigue, and also conditions the drum surface for easy removal of the toner particles remaining on the surface of the electroplate after transfer.

- The xerographic toner images transferred onto the surface of print receiving web 24 may be affixed thereto by any one of several known methods which include fixing by pressure, heat and toner chemical solvent. Pressure fixing rollers within unit 31 are employed in the preferred embodiment of this invention, and a sufiicient line contact pressure of approximately 500 pounds per lineal inch of contact is employed to cause the xerographic toner supported by the surface of the web to flow into the fibers thereof. In order to assure that the web is not torn or mutilated by being pulled through the pressure fixing rollers (not shown), the rollers are connected to the main drive mechanism 13 so as to be rotated in step with movement of xerographic drum 11..

Latent electrostatic image formation As stated previously, a latent electrostatic image of matter to be printed or copied, is'created in an electrically insulating, dielectric layer by producing electrostatically charged areas thereon. This may be done in any one of several ways. For instance, the photoconductive insulating layer 17 (Fig. 1) may initially be charged positive, for example, by an ion-producing unit 119, and thereafter while still charged may be exposed to an optical image formed by passing light rays through an opaque-transparent image defining stencil. As a result, a positively charged latent electrostatic image will be produced in photoconductive insulating layer 17 for the reasons that those electrically charged incremental areas of the photoconductive layer onto which light rays are di- Optical recorder.The xerographic printer shown in Fig. 1 may be employed as a record card controlled lineby-line optical data recorder by forming lines of character images on the surface of electroplate 16. The image producing apparatus for such a line-by-line optical recorder, is similar to that shown and described in copending U.S. patent application, Serial No. 466,496, filed by E. Buhler on November 3, 1954, now U.S. Patent 2,726,940, issued on December 13, 1955. Inasmuch as the apparatus for producing the line-by-line latent electrostatic images optically is not per se a part of the present invention, the same will be described but briefly with reference to Figs. 2 and 3. A more detailed description is available in the afore-mentioned copending Buhler application.

Referring to Fig. 3, a constantly rotating drum 41 is provided with rows and columns of transparent characters 42 (see also Fig. 2) on an opaque background 43. To facilitate illustration, the background is shown to be light'and the characters are dark, but it will be understood that the characters are transparent. An individual column of characters 42 spaced around the periphery of drum 41, is associated with each of eighty possible print positions, one for each column of the well-known eighty column IBM record card. A plurality of are units 44 each comprising a plurality of electrodes 20, 30 and 40, are mounted inside drum 41 and are so aligned that there is one are unit behind each column of characters 42. The electrodes 30 and 40 are arcing electrodes and elec- 'trode 20 is a triggering electrode that is used to alter the breakdown characteristic of the gap between electrodes 30 and 40 to initiate arcing. Opaque barriers (not shown) are interposed between adjacent are units and serve the dual purpose of preventing any possible tendency of the discharge of one are to cause the discharge of an adjacent arc, and of preventing the illumination produced by one are from falling upon a character 42 associated with an adjacent arc unit. Reference may be had to the copending F. Demer et al. U.S. Patent application, Serial No. 203,747, filed on December 30, 1950, now U.S. Patent No. 2,714,841 issued August 9, 1955, for a detailed disclosure of the arc unit.

Adjacent the drum 41 and in alignment with each are unit 44 corresponding to each column of characters 42, are individual focusing lenses 46. A plurality of socalled zoning slots 47 are arranged in five columns on one end of drum 41, which slots cooperate with five light sources (not shown) that are mounted inside drum 41 and with five photocells 48. It is to be observed that a given character 42 and a corresponding zoning slot 47 pass respective arc unit 44 and phototubes 48 at the same time. The preceding elements cooperate to emit timed pulses which are adapted by suitable circuits rep resented by block 57 to cooperate with other timed pulses derived from the sensing of the aforementioned record cards 45, so as to efi'ect a selective triggering of the individual are units 44 as select characters 42 pass between their are units and respective focusing lenses 46. As a result, a character shaped light beam will be passed through a lens 46. A photoemissive material plate 49 is arranged to be exposed to the light emitted from an arc unit, shaped by the character stencil and passed through a corresponding lens 46. Hence, upon exposure to light, the plate 49 will emit a cloud of electrons whose cross-sectional configuration is similar to that of the shaped light beam passing through its lens 46. These electrons are attracted toward a high potential plate 51 connected to battery 55. A web 52 made of dielectric material is interposed between photoemissive plate 49 and high potential plate 51 so that as the electrons emitted from plate 49 are attracted toward the high potential plate 51, they are deposited on web 52 as a latent electrostatic image of the corresponding optical image. The web 52 of dielectric material is thereafter passed through a toner image developing chamber 58 whereat the latent units 53.

In summation, a latent electrostatic image of a character 42 on the periphery of drum 41 is caused to be formed when corresponding data representing pulses from photocells 43 and record card reading station 54 operate circuits represented by block 56 which, in turn, effect the operation of associated arc control circuits 57 in order to fire select are units 44. That is, assuming that record card sensing brush 37 for reading the second card column, detects punched holes indicative of the letter A, this information will be stored in circuits 56. Thereafter, when phototubes 48 detect zoning slots 47 which are also indicative of the letter A '(it will be recalled that at this time the corresponding characters 42, i.e., the letter A, are aligned with their respective are units 44), the coincidence of information from .photo tubes 48 and the second record card column will cause a triggering signal to be directed from circuits 57 via line 38 to electrode 20 of the arc unit 44 associated with the second record card column. The ensuing arc will cause a latent image of a letter A to be formed on dielectric web 52 at a position aligned with the arc unit 44 that was fired. Other latent images may be formed in a similar fashion, and then may be developed and fixed as afore-described.

Non-optical rec0rder.-The non-optical, line-by-line Xerographic printer of this invention does not require an ion-producing unit for precharging the electroplate for reasons to become clear shortly. A stencil cylinder 61 (see also Fig. 4) and associated apparatus would replace previously described cylinder 41 and its associated apparatus (Fig. 3), and would be continuously rotated by drive mechanism 13 (Fig. 1) so that the stencil cylinder would complete a single revolution for each aforementioned line-by-line movement of Xerographic drum 11. The Xerographic drum is also driven by drive mechanism 13, but via a conventional Geneva mechanism 14. It is by way of the Geneva mechanism 14 that the continuous rotational movement of the stencil cylinder is correlated to the step-by-step movement of xerographic drum 11. Referring to Fig. 4, stencil cylinder 61 is a somewhat thin-walled conductor supported at each end by two hubs (not shown) which may be rotated about a stationary hollow shaft 62 through which wires are passed. The preferred embodiment of this invention in cludes a stencil cylinder having eighty columns of circumferentially disposed characters 63 (see also Fig. 4), one for each column of the well-known IBM record card, which eighty columns of characters are identical and are similarly disposed to provide rows of identical characters extending lengthwise on the periphery of the drum. The characters might be comprised of a plurality of holes as depicted by stencils 63a (Fig. 6) or a plurality of prearranged slits as depicted by stencils 63b.

Secured to stationary hollow shaft 62 within cylinder 61 is a single corona discharge unit 64 including a corona wire 66 which runs the length of cylinder 61. As a result, when electrical power is applied to wire 66, a corona field discharge is directed through a channeled opening 67 in unit 64, which extends the full length of cylinder 61, towards the inner surface of stencil cylinder 61. Normally, this corona field discharge is prevented from passing through the stencil characters in stencil cylinder 61 for the reason that all eighty pairs of control electrodes 68 (see also Fig. 5) associated with each columnar position of stencil drum 61, are normally biased electrically to a potential of approximately 800 volts. Connecting wires for each of these control electrodes are shown in Fig. 5, and are run within hollow shaft 62. Thus, since the conductive backing member 18 (see also Fig. 1) is at ground potential, as mentioned previously, and inasmuch as the corona field discharge from unit 64 (Fig. 3) is a positive one, the

7 field discharge will normally be divided into approximately 160 separate paths which include the eighty pairs of highly negative control electrodes 68 (Fig. It should be pointed out that electrostatic field barrier plates (not shown) are used to divide opening 67 into eighty separated openings corresponding to the number of characters on stencil cylinder 61. This is to prevent a lateral deflection of the corona discharge field from one character position to another position. At a time that a select character stencil 63 is aligned with the channeled opening 67 in unit 64, a positive potential in the order of approximately +800 volts is caused to be applied to the pairof corresponding character position control electrodes 68. This action causes the positive corona field discharge to pass through the opening 67 defined by the afore-mentioned electrostatic barrier plates and the oppositely placed columnar control electrodes 68 each of which is raised to +800 volts, through the character stencil 63 aligned therewith, and onto the previously uncharged surface of the dielectric layer 17 (Fig. 1) on electroplate 16. The aforementioned barrier plates (not shown) will restrict such a field to a region opposite the select character stencil. During a complete revolution of cylinder 61, a line of characters as depicted by latent electrostatic images thereof may be formed before the xerographic drum 11 is advanced one line position. This non-optical Xcrographic recorder might be a record card controlled machine governed in a manner similar to the way in which the optical recorder (Figs. 2 and 3) is governed. That is consequent upon the coincidence of record card indicia and zoning slot data generated as a result of the position of the stencil cylinder 61 (Fig. 5) relative opening 67, a suitable negative voltage generator would be triggered off and a positive voltage generator triggered on. There would be one such positive voltage generator as well as one such negative voltage generator for each character position, i.e., for each pair of control electrodes 68. Connections from these generators to the control electrodes would be completed via the wires within hollow shaft 62. As stated previously, it is within the concept of this invention to provide such a non-optical line-by-line printer which would transcribe data directed from a calculator. Thus, consequent upon the coincidence of calculator output data signals and zoning slot data generated as a result of the position of the stencil cylinder 61 relative opening 67, a suitable positive voltage would be applied to a pair of control electrodes 68.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art,

Without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a Xerographic printer comprising a xerographic member having an insulating surface layer adapted to have electrostatic images formed thereon, means for producing electrostatic images on said layer comprising in combination a continuously rotatable conductive cylinder having a plurality of columns of different beam shaping stencil characters; means located within said cylinder for producing a continuous electrostatic field discharge beam substantially coextensive with and radiating outward said cylinder for passage through said stencil characters; means for controlling the formation of discrete select character shaped electrostatic beams from said, continuous beam during transit of said columns of said stencil characters including a plurality of pairs of electrodes equal in number to the number of columns of said stencil characters, each of said pairs of electrodes being located in spaced apart relation intermediate said continuous beam producing means and said cylinder at positions corresponding to said columns, and control means connected to said pairs of electrodes normally operable for directing said continuous beam onto said electrodes and selectively operable for deflecting select portions of said continuous beam onto corresponding select areas of said cylinder for passage through select stencil characters.

2. In a xerographic printer comprising a xerographic member having an insulating surface layer adapted to have electrostatic images formed thereon, means for producing electrostatic images on said layer in accordance with claim 1, wherein said continuous beam forming means comprises a continuous conductor adapted to generate a corona discharge field and means forming a channeled opening for directing said corona field between said plurality of pairs of electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 2,676,100 Huebner Apr. 20, 1954 2,714,841 Demer et al. Aug. 9, 1955 2,726,940 Buhler Dec. 13, 1955 2,756,676 Steinhilper July 31, 1956 2,777,745 McNaney Jan. 15, 19 57 

